Hybrid silicon-containing coupling agents for filled elastomer compositions

ABSTRACT

This invention describes novel chemical compounds whose structures are hybrids between sulfur-containing and non-sulfur-containing silanes wherein the two types of silanes are linked by siloxane bonds. The invention includes methods of preparation for the hybrid silanes as well as their use in filled rubbers as coupling agents. The hybrid silanes described are unique in that a certain amount of water in their preparation leads to superior performance in their intended application, and that they can thus be produced more efficiently and safely than coupling agents currently used in the art, from readily available hydrated raw materials.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.10/137,463 filed on Apr. 30, 2002, (now U.S. Pat. No. 7,169,872) whichclaims benefit of provisional application 60/287,888 filed on Apr. 30,2001, the disclosure of each is incorporated herein by reference in isentirety.

FIELD OF THE INVENTION

This invention relates to silane coupling agents for use in filledelastomer compositions, and in particular, rubber compounding. Thecoupling agents of the present invention are distinguished in that theirmolecular structure is a hybrid of two structural entities, eachcontaining a unique type of silicon ultimately uniting polymer andfiller in the final composition.

BACKGROUND OF THE INVENTION

The vast majority of prior art in the use of coupling agents in rubberinvolves silane molecules containing one or two, and in less frequentcases, up to several silicon atoms bound to any one of a wide number ofsulfur-functional groups. Each silicon is almost exclusively bound toone or more simple hydrolyzable alkoxy group in the practiced art.Sulfur is indirectly bonded to the silicon chemically via a backbone ofone to several carbon atoms. These sulfur silane coupling agentsfunction by chemically bonding silica to polymer used in rubberapplications in a relatively simple and straight forward manner.Coupling is accomplished by chemical bond formation between the silanesulfur and the polymer and by hydrolysis of the silane alkoxy groups andsubsequent condensation with silica hydroxyl groups.

Commonly used coupling agents typically contain silicon exclusivelybound to carbon and alkoxy groups, and need to be manufactured usinganhydrous alcoholic solutions of sulfur anions of alkali metal ions orthe ammonium ion. Anhydrous materials must be used so as to preserve thehydrolytically labile alkoxy groups present on silicon. Despite the lowcost and general availability of hydrated sodium sulfide, polysulfide,and hydrosulfide salts, anhydrous analogs are not easily obtained orhandled because of their great affinity for water. The removal of waterfrom hydrous materials requires conditions conducive to fire hazards andusually does not go to completion. Preparations of anhydrous materialsby indirect methods are costly and involve raw materials, such asmetallic sodium and hydrogen sulfide, which pose special hazards duringuse and transportation. Thus, it would be beneficial from a safety andeconomic standpoint to use starting materials which do not requireanhydrous conditions or reagents.

The use of mixtures of separate silicones and sulfur silanes in tireapplications is known in the art and for instance, is described inEuropean Patent EP 0 784 072 A1 wherein individual silicon containingchemical compounds are blended, either prior to incorporation into therubber compound, or by being sequentially added to the rubber compound.Thus, it would be advantageous to have a single compound which providesthe benefits obtainable from the separate silicones and sulfur silanesthereby eliminating additions during the rubber compounding.

Bearing in mind the problems and deficiencies of the prior art, it istherefore an object of the present invention to provide a sulfur silanewhich can be made under non-anhydrous conditions.

It is another object of the present invention to provide a sulfur silanehaving the advantages of a both a sulfur containing silane and asilicone.

SUMMARY OF THE INVENTION

The silicon-containing chemical compounds of the present invention,hereinafter referred to as “hybrid silane compositions”, are novelhybrid sulfur silane coupling agents. They are comprised ofdistributions of novel molecules, herein referred to as “hybridsilanes”, which are siloxane hybrid molecules of two distinct types ofalkoxy silanes. The hybrid silanes are hybrids in the sense that one ormore pairs of alkoxy groups, one each from a silicon atom of each of thetwo alkoxy silane types, have been replaced by an equal number (i.e.,number of oxygen atoms equals the number of pairs of alkoxy groups) ofoxygen atoms, which bridge the originally separate structures into asingle molecule, via an equal number (i.e., number of new Si—O—Silinkages equals the number of pairs of alkoxy groups) of new Si—O—Silinkages. The two aforementioned distinct types of alkoxy silanes aresulfur-containing alkoxysilanes, herein referred to as “sulfur silanes”,and hydrocarbon-functionalized alkoxysilanes, herein referred to as“alkylalkoxysilanes”.

The hybrid silane compositions optionally also contain the individualsulfur silanes and alkylalkoxysilanes, themselves; partial or fullcondensation products of the individual sulfur silanes; and partial orfull condensation products of the individual alkylalkoxysilanes. Thehybrid silanes exhibit advantages both in use and from a manufacturingstandpoint over conventional sulfur-containing alkoxysilanes, such asTESPT and TESPD (the nominal triethoxysilylpropyl tetrasulfide andtriethoxysilylpropyl disulfide, respectively), currently being used inthe tire and rubber industry.

The present invention further relates to a novel process formanufacturing the hybrid silanes wherein the presence of water is notonly tolerated, but moreover sought, leading to a safer process andlower cost product.

In addition, the present invention further relates to the use of thehybrid silanes in a rubber composition, particularly useful in tires,wherein the rubber composition comprises at least one crosslinkablerubber and a filler.

The crosslinkable rubber is preferably a conjugated diene homopolymer orcopolymer, or a copolymer of at least one conjugated diene and aromaticvinyl compound. The filler is preferably at least one of siliceousfillers; carbon black; clays; inorganic oxides such as alumina andtitania, and their silicates; and multiple phase fillers composed ofindividual phases of the aforementioned fillers, such as carbon-silicadual phase fillers. The filler is more preferably a mixture of suchfillers such as carbon black or carbon black and at least one siliceousfiller.

The use of these silanes in the manufacture of inorganic filledelastomers is taught wherein processing advantages and/or more desirableend products are realized, which can be achieved with neither theindividual structural components of the hybrid silanes alone, nor withmere mixtures of these structural components.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENT(S)

The hybrid silanes of the present invention are sulfur silane-siliconehybrids useful as coupling agents for elastomers and fillers. The hybridsilanes described in the present invention are composed of singlecomponents or mixtures of molecules whose individual chemical structurescan be represented by the following general formula,F¹ _(r)F² _(s)  Formula (I)wherein

r is 0 to 10,000;

s is 0 to 10,000;

F¹ has one of the general structures,{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R²_(n)Si-G¹-S_(x)—(C=E)_(y)-E_(z)}_(p)-G²  Formula (II)or{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R² _(n)Si-G¹-S_(x)—}₂(C=E)_(y)  Formula(III)wherein

each occurrence of R¹ and R² is independently hydrogen, or any groupwhich can be obtained by removal of one hydrogen atom from a hydrocarbongroup having from 1 to 20 carbon atoms, including branched or straightchain alkyl, alkenyl, aryl or aralkyl groups;

each occurrence of G¹ is any group which can be obtained by removal of aquantity of two hydrogen atoms from any hydrocarbon having from 1 to 20carbon atoms;

each occurrence of G² is independently a hydrogen atom or any groupwhich can be obtained by removal of a quantity of p hydrogen atoms fromany hydrocarbon having from 1 to 20 carbon atoms;

S is sulfur;

O is oxygen;

Si is silicon;

each occurrence of E is independently oxygen or S_(x);

each occurrence of m and n is independently 0, 1 or 2;

each occurrence of p is independently 1 to 4;

each occurrence of y and z is independently 0 or 1; and

each occurrence of x is independently 1 to 8;

F² is represented by the general structure:(R¹O)_(4-m′-n′)[(—O—)_(0.5)]_(m′)R³ _(n)Si  Formula (IV)wherein

each occurrence of R¹ is as defined above;

each occurrence of R³ is independently hydrogen, or a hydrocarbon groupof 1 to 20 carbon atoms including aryl as well as branched or straightchain alkyl, alkenyl, arenyl, or aralkyl groups; and

each occurrence of m′ and n′ can be independently 0, 1, 2 or 3.

It is also possible that m′ may be 4, but with the provisos that 1) thequantities of silicon atoms when m′ is equal to 4 are not aggregatedtogether in quantities in excess of that which would arise from thesynthetic methods described below, 2) that the product is prepared byone of the methods described below, and 3) that silica is not used as araw material in the manufacturing process, which would give rise toaggregates of silica in which m′ is equal to 4.

The hybrid silane compositions of the present invention are furthercharacterized in that they are comprised of at least one hybrid silane;that is, they are comprised of at least one chemical compound in which rand s of Formula (I) above each have a value of at least 1.

All G¹ and all G² containing at least one carbon atom are hereinreferred to as divalent hydrocarbon groups and p-valent hydrocarbongroups, respectively. Thus, as used herein, a divalent hydrocarbon groupis understood to mean any hydrocarbon from which a quantity of twohydrogen atoms have been removed and a p-valent hydrocarbon group isunderstood to mean any hydrocarbon from which a quantity of p hydrogenatoms have been removed.

The F¹ and/or F² components of any of the structures given by Formula(I) are chemically linked by a quantity of Si—O—Si bonds given by (m andm′)/2. In each of these Si—O—Si bonds, an oxygen atom is bonded to twosilicon atoms. Each of these two silicon atoms occurs in one of each F¹or each F². Each of the oxygen atoms in any of the structures given byFormula (I) constitutes a chemical link (Si—O—Si bond) between siliconatoms of F¹ and F²; between silicon atoms of F¹ and another like ordifferent F¹; between silicon atoms of F² and another like or differentF²; or between two silicon atoms within a single F¹. The hybrid silanecompositions of the present invention comprise at least one hybridsilane whose structure according to Formula (I) contains at least oneSi—O—Si bond between one silicon atom of a structure given by F¹ and onesilicon atom of a structure given by F². In practice the hybrid silanecompositions, although they need not, often will contain many hybridsilanes whose structures according to Formula (I) contain more than oneSi—O—Si bond between silicon atoms of structures given by F¹ and siliconatoms of structures given by F², as well as silanes whose structuresaccording to Formula (I) contain Si—O—Si bond(s) between silicon atomswithin the same or from two like or different structures given by F¹alone, as well as siloxanes whose structures according to Formula (I)contain an Si—O—Si bond between silicon atoms from two like or differentstructures given by F¹ alone. In addition, the hybrid silanecompositions of the present invention may, but need not, containcomponents whose structures given by F¹ and F² contain no Si—O—Si bond;that is, structures wherein m and m′, respectively, are zero. Thesestructures would correspond to individual molecules of sulfur silane andalkylalkoxysilane, respectively.

The structures of F¹ are molecular fragments derived fromsulfur-containing alkoxysilanes in which a quantity m of the alkoxygroups have been removed. Thus, when m is 0, the structure of F¹ wouldrepresent a sulfur-containing alkoxysilane. Any such m is 0 specie willhereinafter be referred to as a “sulfur silane”. An analog species wherem is greater than 0 will hereinafter be referred to as a “sulfur silanecondensate”.

The structures of F² are molecular fragments derived from hydrocarbongroup-containing alkoxysilanes in which a quantity m of the alkoxygroups have been removed. Thus, when m is equal to 0, the structure ofF² would represent a hydrocarbon group-containing alkoxysilane. Any suchm is equal to 0 specie will hereinafter be referred to as an“alkylalkoxysilane”. An analog species where m is equal to 0 willhereinafter be referred to as an “alkylalkoxysilane condensate”. Anymember of the group collectively consisting of the structures for F¹ andF² when m is equal to 0 will herein be referred to as an “alkoxysilane”,and similarly, any member of the group collectively consisting of thestructures for F¹ and F² when m is greater than 0 will herein bereferred to as an “alkoxysilane condensate”.

As used herein, alkyl includes straight, branched and cyclic alkylgroups; alkenyl includes any straight, branched, or cyclic alkenyl groupcontaining one or more carbon-carbon double bonds, where the point ofsubstitution can be either at a carbon-carbon double bond or elsewherein the group; and alkynyl includes any straight, branched, or cyclicalkynyl group containing one or more carbon-carbon triple bonds andoptionally also one or more carbon-carbon double bonds as well, wherethe point of substitution can be either at a carbon-carbon triple bond,a carbon-carbon double bond, or elsewhere in the group. Specificexamples of alkyls include methyl, ethyl, propyl, isobutyl. Specificexamples of alkenyls include vinyl, propenyl, allyl, methallyl,ethylidenyl norbornane, ethylidene norbornyl, ethylidenyl norbornene,and ethylidene norbornenyl. Specific examples of alkynyls includeacetylenyl, propargyl, and methylacetylenyl. As used herein, arylincludes any aromatic hydrocarbon from which one hydrogen atom has beenremoved; aralkyl includes any of the aforementioned alkyl groups inwhich one or more hydrogen atoms have been substituted by the samenumber of like and/or different aryl (as defined herein) substituents;and arenyl includes any of the aforementioned aryl groups in which oneor more hydrogen atoms have been substituted by the same number of likeand/or different alkyl (as defined herein) substituents. Specificexamples of aryls include phenyl and naphthalenyl. Specific examples ofaralkyls include benzyl and phenethyl. Specific examples of arenylsinclude tolyl and xylyl. As used herein, cyclic alkyl, cyclic alkenyl,and cyclic alkynyl also include bicyclic, tricyclic, and higher cyclicstructures, as well as the aforementioned cyclic structures furthersubstituted with alkyl, alkenyl, and/or alkynyl groups. Representiveexamples include norbornyl, norbornenyl, ethylnorbornyl,ethylnorbornenyl, ethylcyclohexyl, ethylcyclohexenyl,cyclohexylcyclohexyl, and cyclododecatrienyl.

Representative examples of sulfur silanes of the present invention, F¹(i.e., with m=0), include bis-(3-triethoxysilyl-1-propyl)thioether,bis-(3-triethoxysilyl-1-propyl)disulfide,bis-(3-triethoxysilyl-1-propyl)trisulfide,bis-(3-triethoxysilyl-1-propyl)tetrasulfide (TESPT),bis-(3-triethoxysilyl-1-propyl)pentasulfide,bis-(3-triethoxysilyl-1-propyl)hexasulfide,bis-(3-triethoxysilyl-1-propyl)heptasulfide,bis-(3-triethoxysilyl-1-propyl)octasulfide, or any mixtures thereof;bis-(triethoxysilylmethyl)disulfide,bis-(triethoxysilylmethyl)tetrasulfide;bis-(2-triethoxysilyl-1-ethyl)disulfide,bis-(2-triethoxysilyl-1-ethyl)tetrasulfide,bis-(1-triethoxysilyl-1-ethyl)disulfide,bis-(1-triethoxysilyl-1-ethyl)tetrasulfide,bis-(3-triethoxysilyl-1-propyl)dithiocarbonate,bis-(3-triethoxysilyl-1-propyl)trithiocarbonate,bis-(3-trimethoxysilyl-1-propyl)tetrasulfide, andbis-(3-triisopropoxysilyl-1-propyl)disulfide.

Representative examples of alkylalkoxysilanes of the present invention,F² (i.e., with m=0), include tetraethoxysilane, tetramethoxysilane,triethoxysilane, tetraisopropoxysilane, tetrapropoxysilane,methyltriethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane,propyltriethoxysilane, propyltrimethoxysilane, phenyltriethoxysilane,phenyltrimethoxysilane, octyltriethoxysilane, octyltrimethoxysilane,octadecyltriethoxysilane, and octadecyltrimethoxysilane.

Representative examples of R¹ include methyl, ethyl, propyl, isopropyl,butyl, phenyl, and benzyl. Methyl, ethyl, and isopropyl are preferred.Ethyl is most preferred. Representative examples of R² include hydrogen,methyl, ethyl, propyl, isopropyl, sec-butyl, phenyl, vinyl, cyclohexyl,and higher straight-chain alkyl, such as butyl, hexyl, octyl, lauryl,and octadecyl. Methyl, ethyl, phenyl, and the higher straight-chainalkyl are preferred. Methyl and phenyl are most preferred.Representative examples of R³ include hydrogen, methyl, ethyl, propyl,isopropyl, sec-butyl, phenyl, vinyl, cyclohexyl, and higherstraight-chain alkyl, such as butyl, hexyl, octyl, lauryl, octadecyl,ethylcyclohexyl, ethylnorbornyl, ethylcyclohexenyl, ethylnorbornenyl,divinylcyclohexylethyl, and phenethyl. Methyl, ethyl, phenyl, and thehigher straight-chain alkyl are preferred. Methyl, octyl, octadecyl, andphenyl are most preferred.

Representative examples of G¹ include —CH₂—, —CH₂CH₂—, —CH₂(CH₂)_(a)CH₂—in which the quantity, a, is an integer of from 1 to 16, -phenylene-,—CH₂-phenyl-, —CH₂CH₂-phenyl-, and —CH(CH₃)—. The structures, —CH₂—,—CH₂CH₂—, and —CH₂(CH₂)_(a)CH₂— in which the quantity, a is 1 or 2 arepreferred. The structures, —CH₂— and —CH₂CH₂CH₂— are most preferred.

Representative examples of G² include those listed for G¹ and alsoinclude —CH₂(—CH)CH₂—, and any of the isomers of —CH₂CH-(cyclohexyl)-,—CH₂CH-(cyclohexanol)-, and —CH₂CH-(norbornenyl)-.

The preferred embodiments of the present invention include mixtures ofsilicon-containing chemical compounds of Formula (I) in which: thesulfur silane condensates are derived from any of thebis-(3-triethoxysilyl-1-propyl) thioether or polysulfides wherein thequantity, x, of Formulae (II) and (III) is 1 to 8, any of thebis-(triethoxysilylmethyl) thioether or polysulfides wherein thequantity, x, of Formulae (II) and (III) is 1 to 8, or any of thebis-(triethoxysilylethyl) thioether or polysulfide isomers wherein thequantity, x, of Formulae (II) and (III) is 1 to 8 by loss of one or moreethoxy groups, and in which the alkylalkoxy silane condensates arederived from tetraethoxysilane, tetramethoxysilane,methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane,phenyltriethoxysilane, octyltriethoxysilane, and/oroctadecyltriethoxysilane by loss of one or more ethoxy groups.

There are two key components for any method to prepare any of thechemical compositions of the present invention. The first is the use ofalkoxysilane starting materials and the presence of water to effectpartial hydrolysis of silane alkoxy groups and subsequent or concurrentcoupling of the silane groups via Si—O—Si linkages. These Si—O—Silinkages derive their silicon atoms from the original alkoxysilanes andthe O atoms from the water used in the process. The conversion of thestarting alkoxysilane bonds to Si—O—Si can be brought to completion, butis preferably brought to only partial completion by limiting thequantity of water introduced into the process. Partial completioninsures that alkoxy groups will remain on silicon in the finalcomposition, which facilitate eventual coupling to the fillers used withthe present compositions in their intended application. The water usedin the preparation of the compositions of the present invention can bewater per se, water in the form of a hydrated chemical species or salt(e.g., hydrated sodium sulfide), or water which has been used to couplesilicon atoms to form Si—O—Si bonds via a previous process. Thus, in thelast process, water could, for example, be added in the form of asiloxane or silicone oil. In such a process, the silicone oil would,itself, have been derived by reacting a silane containing hydrolyzablegroups such as, but not limited to alkoxysilanes with water.

The second key component for any preparation of the chemicalcompositions of the present invention is the use of a sulfur anion todisplace a leaving group from a carbon atom, by a chemical reaction,herein referred to as a sulfur anion displacement reaction. The sulfuranion displacement reaction, typically but not necessarily anucleophilic displacement reaction, is shown below in Equations I and IIfor the preparation of the hybrid silanes whose structures are given byFormulae (II) and (III), respectively:2(R¹O)_(3-m-n)R² _(n)Si-G¹-L+Nuc1→[(R¹O)_(3-m-n)R²_(n)Si-G¹-S_(x)—]₂(C=E)_(y)+2L⁻  Equation Ip(R¹O)_(3-m-n)R² _(n)Si-G¹-L+Nuc2→[(R¹O)_(3-m-n)R²_(n)Si-G¹-S_(x)—(C=E)_(y)-E_(z)-]_(p)G² +pL⁻  Equation II

Anions corresponding to L may be chloride, bromide, iodide, sulfate, andany of the sulfonates such as but not limited to tosylate,benzenesulfonate, and triflate, with chloride being preferable due tocommercial availability. Bromide is preferable in cases where anenhanced reactivity relative to the chloride is desired, such as inaromatic halogen substitutions, which require driving conditions. Nuc1and Nuc2 are sulfur anions which can be represented by the structuresgiven by Formula (V) and Formula (VI), respectively, or, in the case ofFormula (VI), their partially but not fully protonated derivatives.Nuc1=(⁻S_(x))₂(C=E)_(y)  (Formula V)Nuc2=[⁻S_(x)—(C=E)_(y)-E_(z)-]_(p)G²  (Formula VI)

E, and the quantities, x, y, z, and p are defined as above.

Examples of Nuc1 and Nuc2 would include, but are not limited to sulfide,disulfide, trisulfide, tetrasulfide, pentasulfide, hexasulfide,heptasulfide, octasulfide, hydrosulfide, trithiocarbonate, anddithiocarbonate, and any of the thiocarboxylates and dithiocarboxylates.Other examples would include the polysulfide analogs oftrithiocarbonate, dithiocarbonate, and any of the thiocarboxylates anddithiocarboxylates; i.e. structures of Formula (4) in which x and/or zis greater than 1.

Particularly useful sulfur anions include sulfide, polysulfide (whichoccur as mixtures of sulfide, disulfide, and trisulfide, tetrasulfide,etc.), hydrosulfide, trithiocarbonate analogs containing fewer thanthree sulfur atoms (hereafter referred to collectively asthiocarbonates), and so forth. Sodium sulfide is commercially availableas a hydrate containing about 40% by weight of water. Hydrated sodiumhydrosulfide, NaSH, is similarly available. It can also be generated byaddition of hydrogen sulfide to solutions of sodium sulfide preparedfrom the readily available sodium sulfide described above. Hydratedsodium polysulfides are readily available and can also be readilyprepared by the addition of elemental sulfur to solutions of hydratedsodium sulfide. The thiocarbonates can readily be prepared from hydratedsodium sulfide by addition of such readily available materials as carbondisulfide, carbonyl sulfide, and/or carbon dioxide. The thiocarbonatescan be further converted to their respective polysulfidic analogs byaddition of elemental sulfur. All of the aforementioned materials inanhydrous form, however, are difficult to prepare because of their greataffinity for water and chemical reactivity. Hydrous NaSH loses hydrogensulfide and forms sulfide salts with attempts to drive off the waterthermally and/or with a vacuum. Anhydrous sodium sulfide oxidizes in airwith sufficient ease, especially at the elevated temperatures requiredto drive off the water, so as to be pyrophoric. The polysulfide saltsare more stable, and can be substantially dehydrated, but alkoxysilanederivatives prepared from them in otherwise anhydrous media alwayscontain higher concentrations of Si—O—Si condensation products than dothe derivatives prepared from polysulfide salts which were themselvesprepared in anhydrous media, thereby demonstrating that some wateralways remains with any reasonable attempts to drive the water fromhydrous polysulfide salts thermally. Since the thiocarbonates areprepared from sulfide salts, they would also only be readily availableonly as hydrates.

The present invention includes a particularly efficient method of usingcoupling agents for elastomers. Anhydrous salts of sulfur anions neednot be used. In fact, the readily available hydrous salts are preferablefor use in the preparation of the chemical compositions of the presentinvention due to the presence of Si—O—Si bonds in their structure whichare derived from the water present in the hydrous salts of the sulfuranions used to prepare them. The inclusion of water distinguishes overother methods that exclude water. By incorporating water with the helpof the alkylalkoxysilanes into the very structure of the coupling agent,two advantages are realized: 1) the chemical compositions of the presentinvention enhance processability and/or properties of rubbercompositions over rubber compositions prepared using the analogoussulfur silanes prepared in anhydrous media, and 2) the chemicalcompositions of the present invention can be prepared from readilyavailable hydrous raw materials eliminating the need for costly andhazardous methods required to generate the anhydrous analogs.

Practical methods for the preparation of the compositions of the presentinvention depend on how water is introduced, how much is introduced,when it is introduced, and on the order in which the alkylalkoxysilanesand the sulfur silanes and/or sulfur silane precursors are added.Certain combinations of the above would bring about an apparentexclusion of the alkylalkoxysilanes, F², from the Si—O—Si bonding, thusproducing mixtures of alkylalkoxysilanes and Si—O—Si derivatives ofsulfur silanes, instead of the desired hybrid silanes. Similarly, othercombinations of the above would bring about an apparent exclusion of thesulfur silanes from the Si—O—Si bonding, thus producing mixtures ofsulfur silanes and Si—O—Si derivatives of alkylalkoxysilanes, instead ofthe desired hybrid silanes. Both of these scenarios, however, areresolved by a final scrambling of Si—O—Si/alkoxy bonding at a pointduring or after the completion of both the initial alkoxysilanehydrolysis and sulfur anion displacement reactions. Such scramblingoccurs readily under the reaction conditions, especially in the presenceof acidic or basic substances, and also in the presence of ions andsalts. The final product is therefore, with all three methods, not amixture in which either the alkylalkoxysilane or the sulfur silaneremains totally in the form of an alkoxysilane without involvement inSi—O—Si bonding, but rather, a true hybrid silane.

Hydrous sulfur anions may be dehydrated with one or morealkylalkoxysilanes prior to the sulfur anion displacement reaction.Using this method, a solution of the desired sulfur anion is firstprepared. Hydrous sodium sulfide is dissolved in the alcoholcorresponding to the alkoxy groups present on silicon, or other suitablesolvent such as lower boiling point alcohols including methanol.Additional reagents are then added as appropriate to convert the sulfideanion into the desired anion. Using this method, an excess of hydrogensulfide is used in order to convert the sulfide anion to thehydrosulfide anion from which would generate mercapto functionality inthe hybrid silane. Elemental sulfur converts the sulfide anion to adistribution of sulfide and polysulfide anions which would generatethioether, disulfide, and/or polysulfide functionality in the hybridsilane, the distribution being dependent on how much sulfur was added.Carbon disulfide converts the sulfide anion to the trithiocarbonateanion which would generate trithiocarbonate functionality in the hybridsilane. Carbonyl sulfide and/or carbon dioxide generates anions andhybrid silane functionality analogous to those generated with carbondisulfide, but with one or two of the sulfur atoms replaced by oxygen,thus yielding hybrid silane functionalities such as thiocarbonate,dithiocarbonate, and thiothionocarbonate. Alternatively, a hydrousalkali metal salt of the desired anion could be dissolved in the alcoholdirectly.

Regardless of the method chosen to generate the hydrous alcoholicsolution of the desired sulfur anion, the second step of this methodinvolves adding the desired alkylalkoxy silane, either neat or as analcoholic solution, to the hydrous alcoholic solution of the desiredsulfur anion. A chemical reaction subsequently occurs in which the waterpresent in the solution hydrolyzes the silicon alkoxy groups and bringsabout Si—O—Si coupling. If an excess of the alkylalkoxysilane is addedin this step, all of the water is consumed and a distribution ofalkylalkoxysiloxanes is generated. With an excess of water, all of thealkoxy groups are converted to Si—O—Si groups and/or Si—OH groups, andthe remaining water will then further hydrolyze the alkoxy groups of thesilanes yet to be added. Thus, adding an excess of water results in ahybrid of this method.

With the water partially or completely removed from the sulfur anionsolution, the third step of this method is to add the chloroalkylsilanecorresponding to the sulfur silane desired, whereupon two types ofchemical reactions occur more or less simultaneously: First, thechloride ion leaving group is displaced by the sulfur anion to form thedesired sulfur silane with concomitant co-product salt precipitation,and second, the alkoxy groups of the starting chloroalkyl silane and ofthe generated sulfur silane exchange with the Si—O—Si groups generatedfrom the alkylalkoxy silane in the second step of this method. Althoughchloroalkyl silanes are the most commonly available, the starting silanecould also be functionalized with any other suitable leaving groupinstead of chlorine. The aforementioned chloroalkyl silanes or theiranalogs containing leaving groups other than chloride will hereafter bereferred to as sulfur silane precursors. Upon completion of thereaction, the salt precipitate produced is filtered off, the solvent isremoved by evaporation, and any salt that had been dissolved in thesolvent is then filtered off, leaving the behind the desired hybridsilane.

A second method of preparing the compositions of the present inventioninvolves simultaneous Si—O—Si coupling and sulfur anion displacementreactions. Using this method, a solution of the sulfur anion is preparedas described above. However, using this method, both the sulfur silaneprecursor and the alkylalkoxy silane are added together to the sulfuranion solution, rather than sequentially, allowing the water to directlycouple both types of silanes via Si—O—Si linkages. Scrambling of theSi—O—Si linkages, once formed, can occur as described above, but thecomplete Si—O—Si structure of the hybrid silane is formed immediatelyrather than in a later step.

A third method of preparing the silane-sulfur hybrids of the presentinvention also involves concurrent sulfur silane Si—O—Si coupling andsulfur anion displacement reactions, but subsequently followed bySi—O—Si scrambling with alkylalkoxy silanes Using this method, thesulfur anion solution is prepared as described for the two methodsabove. The second step is the addition of the sulfur silane precursor.As described in the first method above, only one of the two types ofalkoxysilanes is initially added to the sulfur anion solution, and as aresult, the initial Si—O—Si framework generated from the water presentin this solution excludes the other alkoxysilane type. Also as describedin the first method above, an excess of water relative to thealkoxysilane present can bring about complete hydrolysis and Si—O—Sicoupling of the Si alkoxy groups with water left over to couple theother alkoxysilane type so as to effect a hybridization of this methodwith Method 2. The difference is that in Method 3, the sulfur silaneprecursor is initially present to take up the water, instead of thealkylalkoxy silane. The third step is then the addition of thealkylalkoxy silane prior to filtration, solvent removal, and finalfiltration, during which time Si—O—Si scrambling occurs to generate thehybrid silane. A novel feature of Method 3 is that the alkylalkoxysilanecan be added after addition of the sulfur silane precursor, but beforeit has completely reacted, in which the final Si—O—Si framework isgenerated by a combination of direct formation and scrambling ofpreformed Si—O—Si bonds.

A fourth method of preparing the sulfur-silane hybrid of the presentinvention involves what may be referred to as sulfur silane-alkylalkoxysilane (Si—O—Si) scrambling. This method is an adaptation of the firstthree methods described above in which the sulfur silane or itspartially or completely hydrolyzed derivative is initially preparedeither from anhydrous or hydrous reagents, respectively, and optionallyisolated. It is then used as a partial or complete replacement for thesulfur silane precursors in the second step of the methods previouslydescribed above. If used as a complete replacement, the need to performthe first step in the process is eliminated.

The four methods described above are discrete ways of categorizing theprocedure based mainly on the order of addition of the reagents, and onwhat happens chemically as a result of these actions. In practice, anysequence that involves the addition of the sulfur silane precursor andthe alkylalkoxy silane to the non-anhydrous sulfur anion solution willultimately bring about formation of the hybrid silane. The arrangementof the Si—O—Si network to form the hybrid silane occurs mostexpeditiously if an acid or base catalyst is present, and is also aidedby the presence of the salt co-product, either precipitated or insolution. The sulfur anion used as the reagent also makes a goodcatalyst.

Alcohols are typically the preferred solvents because they readilydissolve the sulfur anions, mediate the chemical reactions readily, andlead to coarse precipitates which are readily filtered. Other solvents,however, can be used as well, such as ethers, tetrahydrofuran,polyethers, glyme, diglyme and higher glymes, aromatic solvents such astoluene and xylene providing that the sulfur anion is sufficientlysoluble, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidinone,and so forth. The latter solvent is preferred for substitutions directlyon aromatic rings.

If alcohol solvents are used, the preparation of the hybrid silanes canalso be coupled with a transesterification of the alkoxy group by usingor substituting the solvent with another alcohol at any step prior tosolvent removal. The distillation of the alcohol from the mixture can beaccompanied by an exchange of the alkoxy group on silicon in which it isreplaced by the alkoxy group corresponding to the alcohol solventintroduced. Thus, less volatile alcohols readily displace alkoxy groupscorresponding to the more volatile alcohol groups. The reverse can alsobe accomplished, but requires at least two coupled distillations. Anexample would be the use of methoxy sulfur silane precursors withalkylmethoxy silanes in ethanol, removing the solvent by fractionaldistillation and generating an ethoxy hybrid silane.

The hybrid silanes of the present invention are unique in that theycombine the coupling characteristics of the sulfur silanes with thedispersion characteristic of the alkylalkoxysilanes in a singlemolecule. The hybrid silanes described herein are useful as couplingagents for organic polymers (i.e., rubbers) and inorganic fillers.Unlike the use of mixtures of these types of silanes, in which a givensite on silica contains either a coupling silane or a dispersing silane,the hybrid silanes provide both characteristics at every site, therebyallowing for better incorporation of the filler into the polymer matrixat the molecular level. It is this feature along with the high molecularweights of the hybrid silanes which contribute to the very lowvolatilities, and gives the hybrid silanes certain advantages such asthe ability to bring about lower processing viscosity, better desirablefiller dispersion, less premature curing (scorch), and reduced odor.

Elastomers useful with the coupling agents described herein includesulfur vulcanizable rubbers including conjugated diene homopolymers andcopolymers, and copolymers of at least one conjugated diene and aromaticvinyl compound. Suitable organic polymers for preparation of rubbercompositions are well known in the art and are described in varioustextbooks including The Vanderbilt Rubber Handbook, Ohm, R. F., R.T.Vanderbilt Company, Inc. (1990) and in the Manual for the RubberIndustry, Kemperman, T. and Koch Jr., S., Bayer AG, LeverKusen (1993).

One example of a suitable polymer for use herein is solution-preparedstyrene-butadiene rubber (SSBR). This solution prepared SBR typicallyhas a bound styrene content in a range of about 5 to about 50 wt. %,preferably about 9 to about 36 wt. %. Other useful polymers includestyrene-butadiene rubber (SBR), natural rubber (NR), ethylene-propylenecopolymers and terpolymers (EP, EPDM), acrylonitrile-butadiene rubber(NBR), polybutadiene (BR), and so forth. The rubber composition iscomprised of at least one diene-based elastomer, or rubber. Suitableconjugated dienes are isoprene and 1,3-butadiene and suitable vinylaromatic compounds are styrene and alpha methyl styrene. Polybutadienemay be characterized as existing primarily, typically about 90 wt. %, inthe cis-1,4-butadiene form.

Preferably, the polymer is a sulfur curable rubber. Such diene basedelastomer, or rubber, may be selected, for example, from at least one ofcis-1,4-polyisoprene rubber (natural and/or synthetic, preferablynatural), and preferably natural rubber, emulsion polymerizationprepared styrene/butadiene copolymer rubber, organic solutionpolymerization prepared styrene/butadiene rubber, 3,4-polyisoprenerubber, isoprene/butadiene rubber, styrene/isoprene/butadiene terpolymerrubber, cis-1,4-polybutadiene, medium vinyl polybutadiene rubber (about35 to about 50 wt. % vinyl), high vinyl polybutadiene rubber (about 50to about 75 wt. % vinyl), styrene/isoprene copolymers, emulsionpolymerization prepared styrene/butadiene/acrylonitrile terpolymerrubber and butadiene/acrylonitrile copolymer rubber.

For some applications, an emulsion polymerization derivedstyrene/butadiene (E-SBR) having a relatively conventional styrenecontent of about 20 to about 28 wt. % bound styrene, or an E-SBR havinga medium to relatively high bound styrene content of about 30 to about45 wt. % may be used.

Emulsion polymerization prepared styrene/butadiene/acrylonitrileterpolymer rubbers containing about 2 to about 40 wt. % boundacrylonitrile in the terpolymer are also contemplated as diene basedrubbers for use in this invention.

A particulate filler may also be added to the crosslinkable elastomercompositions of the present invention including siliceous fillers,carbon black, and so forth. The filler materials useful herein include,but are not limited to, carbon black and metal oxides such as silica(pyrogenic and precipitated), titanium dioxide, aluminosilicate andalumina, clays and talc, and so forth.

Particulate, precipitated silica is also sometimes used for suchpurpose, particularly when the silica is used in conjunction with asilane. In some cases, a combination of silica and carbon black isutilized for reinforcing fillers for various rubber products, includingtreads for tires. Alumina can be used either alone or in combinationwith silica. The term, alumina, can be described herein as aluminumoxide, or Al₂O₃. The fillers may be hydrated or in anhydrous form.

The hybrid silane composition(s) may be premixed or pre-reacted with thefiller particles, or added to the rubber mix during the rubber andfiller processing, or mixing stages. If the hybrid silane composition(s)and filler are added separately to the rubber mix during the rubber andfiller mixing, or processing stage, it is considered that the hybridsilane composition(s) then combine(s) in an in-situ fashion with thefiller.

The vulcanized rubber composition should contain a sufficient amount offiller to contribute a reasonably high modulus and high resistance totear. The combined weight of the filler may be as low as about 5 toabout 100 parts per hundred rubber (phr), but is more preferably fromabout 25 to about 85 phr.

Preferably, at least one precipitated silica is utilized as a filler.The silica may be characterized by having a BET surface area, asmeasured using nitrogen gas, preferably in the range of about 40 toabout 600 m²/g, and more usually in a range of about 50 to about 300m²/g. The BET method of measuring surface area is described in theJournal of the American Chemical Society, Volume 60, pg. 304 (1930). Thesilica typically may also be characterized by having a dibutylphthalate(DBP) absorption value in a range of about 100 to about 350, and moreusually about 150 to about 300. Further, the silica, as well as theaforesaid alumina and aluminosilicate, may be expected to have a CTABsurface area in a range of about 100 to about 220. The CTAB surface areais the external surface area as evaluated by cetyl trimethylammoniumbromide with a pH of 9. The method is described in ASTM D 3849.

Mercury porosity surface area is the specific surface area determined bymercury porosimetry. Using this method, mercury is penetrated into thepores of the sample after a thermal treatment to remove volatiles. Setup conditions may be suitably described as using a 100 mg sample;removing volatiles during 2 hours at 105° C. and ambient atmosphericpressure; ambient to 2000 bars pressure measuring range. Such evaluationmay be performed according to the method described in Winslow, Shapiroin ASTM bulletin, pg. 39 (1959) or according to DIN 66133. For such anevaluation, a CARLO-ERBA Porosimeter 2000 might be used. The averagemercury porosity specific surface area for the silica should be in arange of about 100 to about 300 m²/g.

A suitable pore size distribution for the silica, alumina andaluminosilicate according to such mercury porosity evaluation isconsidered herein to be such that about 5% or less of its pores have adiameter of less than about 10 nm, about 60 to 90% of its pores have adiameter of about 10 to about 100 nm, about 10 to 30% of its pores havea diameter at about 100 to about 1,000 nm, and about 5 to 20% of itspores have a diameter of greater than about 1,000 nm.

The silica might be expected to have an average ultimate particle size,for example, in the range of about 10 to about 50 nm as determinedelectron microscopy, although the silica particles may be even smaller,or possibly larger, in size. Various commercially available silicas maybe considered for use in this invention such as, from PPG Industriesunder the HI-SIL™ trademark with designations HI-SIL™ 210, 243, etc.;silicas available from Rhone-Poulenc, with, for example, designation ofZEOSIL™ 1165 MP; silicas available from Degussa-Huels with, for example,designations VN2 and VN3, etc., and silicas commercially available fromHuber having, for example, a designation of HUBERSIL™ 18745.

In compositions for which it is desirable to utilize siliceous fillerssuch as silica, alumina and/or aluminosilicates in combination withcarbon black reinforcing pigments, the compositions may comprise afiller mix of about 15 to about 98 wt. % of the siliceous filler, andabout 2 to about 85 wt. % carbon black, wherein the carbon black has aCTAB value in a range of about 80 to about 150. Alternately, a portionof the carbon black may be a grade with extremely high surface area, upto about 800 m²/g. The weight ratio may range from about 3/1 to about30/1 for siliceous fillers to carbon black. More typically, it isdesirable to use a weight ratio of siliceous fillers to carbon black ofat least about 3/1, and preferably at least about 10/1.

Alternatively, the filler can be comprised of about 60 to about 95 wt. %of said silica, alumina and/or aluminosilicate and, correspondingly,about 40 to about 5 wt. % carbon black. The siliceous filler and carbonblack may be pre-blended or blended together in the manufacture of thevulcanized rubber.

In preparing the rubber compositions of the present invention, one ormore of the hybrid silane compositions are mixed with the organicpolymer before, during or after the compounding of the filler into theorganic polymer. It is preferred to add the hybrid silane composition(s)before or during the compounding of the filler into the organic polymer,because these silanes facilitate and improve the dispersion of thefiller. The total amount of hybrid polysulfide silane compositionpresent in the resulting combination should be about 0.05 to about 25phr, more preferably about 1 to about 10 phr. Fillers can be used inquantities ranging from about 5 to about 100 phr, more preferably fromabout 25 to 80 phr.

In practice, sulfur vulcanized rubber products typically are prepared bythermomechanically mixing rubber and various ingredients in asequentially step-wise manner followed by shaping and curing thecompounded rubber to form a vulcanized product. First, for the aforesaidmixing of the rubber and various ingredients, typically exclusive ofsulfur and sulfur vulcanization accelerators (collectively, curingagents), the rubber(s) and various rubber compounding ingredientstypically are blended in at least one, and often (in the case of silicafilled low rolling resistance tires) two, preparatory thermomechanicalmixing stage(s) in suitable mixers. Such preparatory mixing is referredto as nonproductive mixing or non-productive mixing steps or stages.Such preparatory mixing usually is conducted at temperatures of about140° C. to about 200° C., and for some compositions, about 150° C. toabout 180° C.

Subsequent to such preparatory mix stages, in a final mixing stage,sometimes referred to as a productive mix stage, curing agents, andpossibly one or more additional ingredients, are mixed with the rubbercompound or composition, at lower temperatures of typically about 50° C.to 130° C. in order to prevent or retard premature curing of the sulfurcurable rubber, sometimes referred to as scorching. The rubber mixture,also referred to as a rubber compound or composition, typically isallowed to cool, sometimes after or during a process intermediate millmixing, between the aforesaid various mixing steps, for example, to atemperature of about 50° C. or lower. When it is desired to mold and tocure the rubber, the rubber is placed into the appropriate mold at atemperature of at least about 130° C. and up to about 200° C. which willcause the vulcanization of the rubber by the sulfur-containing groups onthe hybrid silane composition(s) and any other free sulfur sources inthe rubber mixture.

Thermomechanical mixing refers to the phenomena whereby under the highshear conditions in a rubber mixer, the shear forces and associatedfriction occurring as a result of mixing the rubber compound, or someblend of the rubber compound itself and rubber compounding ingredientsin the high shear mixer, the temperature autogeneously increases, i.e.it “heats up”. Several chemical reactions may occur at various steps inthe mixing and curing processes.

The first reaction is a relatively fast reaction and is consideredherein to take place between the filler and the silane alkoxide group ofthe hybrid silane composition(s). Such reaction may occur at arelatively low temperature such as, for example, at about 120° C. Thesecond reaction is considered herein to be the reaction which takesplace between the sulfur-containing portion of the hybrid silanecomposition(s), and the sulfur vulcanizable rubber at a highertemperature, for example, above about 140° C.

Another sulfur source may be used, for example, in the form of elementalsulfur, such as but not limited to S₈. A sulfur donor is consideredherein as a sulfur containing compound which liberates free, orelemental sulfur, at a temperature in a range of about 140° C. to about190° C. Such sulfur donors may be, for example, although are not limitedto, polysulfide vulcanization accelerators and organosilane polysulfideswith at least two connecting sulfur atoms in its polysulfide bridge. Theamount of free sulfur source addition to the mixture can be controlledor manipulated as a matter of choice relatively independently from theaddition of the aforesaid hybrid silane composition(s). Thus, forexample, the independent addition of a sulfur source may be manipulatedby the amount of addition thereof and by the sequence of additionrelative to the addition of other ingredients to the rubber mixture.

A desirable rubber composition may therefore comprise about 100 parts byweight of at least one sulfur vulcanizable rubber selected from thegroup consisting of conjugated diene homopolymers and copolymers, andcopolymers of at least one conjugated diene and aromatic vinyl compound,about 5 to about 100 phr, preferably about 25 to 80 phr of at least oneparticulate filler, up to about 5 phr of a curing agent, and about 0.05to about 25 phr of at least one hybrid silane composition as describedin the present invention.

The filler preferably comprises from about 1 to about 85 wt. % carbonblack based on the total weight of the filler, and about 0 to about 20wt. % of at least one hybrid silane composition(s) based on the totalweight of the filler.

The rubber composition may then be prepared by first blending polymer,filler and hybrid silane composition(s), or polymer, filler pretreatedwith all or a portion of the hybrid silane composition(s) and anyremaining hybrid silane composition(s), in a first thermomechanicalmixing step to a temperature of about 140° C. to about 200° C. for about2 to about 20 minutes, preferably about 4 to about 15 minutes.Additional thermomechanical mixing steps may be performed withintermittent cooling. The cooling may be performed by removal of therubber from the mixer. Optionally, the curing agent is then added inanother thermomechanical mixing step at a temperature of about 50° C.and mixed for about 1 to about 30 minutes. The temperature is thenheated again to between about 130° C. and about 200° C. and curing isaccomplished in about 5 to about 60 minutes.

The process may also comprise the additional steps of preparing anassembly of a tire or sulfur vulcanizable rubber with a tread comprisedof the rubber composition prepared according to this invention andvulcanizing the assembly at a temperature in a range of about 130° C. toabout 200° C.

Other optional ingredients may be added in the rubber compositions ofthe present invention including curing aids, i.e., sulfur compounds,including activators, retarders and accelerators, processing additivessuch as oils, plasticizers, tackifying resins, silicas, other fillers,pigments, fatty acids, zinc oxide, waxes, antioxidants and antiozonants,peptizing agents, reinforcing materials such as, for example, carbonblack, and so forth. Such additives are selected based upon the intendeduse and on the sulfur vulcanizable material selected for use, and suchselection is within the knowledge of one of skill in the art, as are therequired amounts of such additives known to one of skill in the art.

The vulcanization may be conducted in the presence of additional sulfurvulcanizing agents. Examples of suitable sulfur vulcanizing agentsinclude, for example elemental sulfur (free sulfur) or sulfur donatingvulcanizing agents, for example, an amino disulfide, polymericpolysulfide or sulfur olefin adducts which are conventionally added inthe final, productive, rubber composition mixing step. The sulfurvulcanizing agents are used, or added in the productive mixing stage, inan amount ranging from about 0.4 to about 3 phr, or even, in somecircumstances, up to about 8 phr, with a range of from about 1.5 toabout 2.5 phr, sometimes from about 2 to about 2.5 phr being preferred.

Optionally, vulcanization accelerators, i.e., additional sulfur donors,may be used herein. It is appreciated that they may be, for example, ofthe type such as, for example, benzothiazole, alkyl thiuram disulfide,guanidine derivatives and thiocarbamates. Representative of suchaccelerators are, for example, but not limited to, mercaptobenzothiazole, tetramethyl thiuram disulfide, benzothiazole disulfide,diphenylguanidine, zinc dithiocarbamate, alkylphenoldisulfide, zincbutyl xanthate, N-dicyclohexyl-2-benzothiazolesulfenamide,N-cyclohexyl-2-benzothiazolesulfenamide,N-oxydiethylenebenzothiazole-2-sulfenamide, N,N-diphenylthiourea,dithiocarbamylsulfenamide, N,N-diisopropylbenzothiozole-2-sulfenamide,zinc-2-mercaptotoluimidazole, dithiobis(N-methyl piperazine),dithiobis(N-beta-hydroxy ethyl piperazine) and dithiobis(dibenzylamine). Other additional sulfur donors, may be, for example, thiuram andmorpholine derivatives. Representative of such donors are, for example,but not limited to, dimorpholine disulfide, dimorpholine tetrasulfide,tetramethyl thiuram tetrasulfide, benzothiazyl-2,N-dithiomorpholide,thioplasts, dipentamethylenethiuram hexasulfide, anddisulfidecaprolactam.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., a primaryaccelerator. Conventionally and preferably, a primary accelerator(s) isused in total amounts ranging from about 0.5 to about 4 phr, preferablyabout 0.8 to about 1.5 phr. Combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts, about 0.05 to about 3 phr, in order to activate and toimprove the properties of the vulcanizate. Delayed action acceleratorsmay be used. Vulcanization retarders might also be used. Suitable typesof accelerators are amines, disulfides, guanidines, thioureas,thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates.Preferably, the primary accelerator is a sulfenamide. If a secondaccelerator is used, the secondary accelerator is preferably aguanidine, dithiocarbamate or thiuram compound.

Amounts of tackifier resins, if used, may comprise about 0.5 to about 10phr, usually about 1 to about 5 phr. Processing aids may comprise about1 to about 50 phr. Such processing aids can include, for example,aromatic, napthenic, and/or paraffinic processing oils. Anti-oxidantsmay comprise about 1 to about 5 phr. Representative anti-oxidants maybe, for example, diphenyl-p-phenylenediamine and others, for example,those disclosed in the Vanderbilt Rubber Handbook, pgs. 344-346 (1978).Amounts of anti-ozonants may comprise about 1 to about 5 phr. Fattyacids, if used, which can include stearic acid, comprise about 0.5 toabout 3 phr. Zinc oxide may comprise about 2 to about 5 phr. Amounts ofwaxes may comprise about 1 to about 5 phr. Often microcrystalline waxesare used. Peptizers may comprise about 0.1 to about 1 phr and may be,for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.

The rubber composition of this invention can be used for variouspurposes. For example, it can be used for various tire compounds. Suchtires can be built, shaped, molded and cured by various methods whichare known and will be readily apparent to those having skill in suchart.

The examples presented below demonstrate significant advantages with theuse of the hybrid silane compositions described herein relative to theuse of simple polysulfide silanes of the currently practiced art, intheir performance as coupling agents in silica-filled rubber. Table 1,listed in Examples 3 and 4, below, presents the performance parametersof hybrid silane compositions of the present invention and of TESPT, thesilane used in the prior art which has become the industry standard.Scorch times for Silanes 1 and 2 are typically noticeably improvedrelative to the control. The 300% modulus of Silane 1 at both loadingsand of Silane 2 at the lower loading is substantially improved in eachcase, over the control: 14.8, 14.1, and 15.3 megapascals, respectively,versus 12.6 megapascals for the control. Silane 1 imparted a noticeablereduction in the value of Tan Delta at 60° C. relative to the control(0.085 vs. 0.103), which is an indicator for someone skilled in the artfor improved rolling resistance in tire tread applications. In additionto these performance advantages, Silanes 1 and 2 were prepared in onestep, directly from hydrous sodium sulfide, whereas the control must beprepared under the more hazardous and costly anhydrous conditionscurrently practiced in the art.

All references cited herein are incorporated by reference herein intheir entirety. The following nonlimiting examples are furtherillustrative of the present invention, but are in no way intended to beconstrued as limiting the invention in any way.

EXAMPLES Example 1 (Silane 1) Preparation of aTetraethoxysilane-bis-(3-triethoxysilyl-1-propyl)polysulfide HybridSilane Composition

Hydrous sodium sulfide (40% H₂O; 60% Na₂S; 65 g, 0.50 moles) supplied inflake form from Fisher Scientific, and 500 g of absolute ethanol wereintroduced into a 3-liter flask equipped with a reflux condenser. Themixture was maintained under an atmosphere of nitrogen using a nitrogenbubbler. Control of the vacuum was enhanced via a bleeder valve insertedbetween the cold trap and the distillation head. The flask was heatedusing an electric heating mantle regulated by a variable voltagecontroller. The voltage controller was coupled to an electronictemperature regulator responsive to the height of mercury in a mercurythermometer which was inserted directly into the mixture in 3-literflask. The mixture was refluxed with stirring until the flakes haddissolved to give a light yellow-brown, nearly clear solution. Stirringwas accomplished using a Teflon® coated stirring bar to preventadherence of any solution to the bar.

The heating was discontinued and the solution allowed to cool to 40° C.,whereupon powdered sulfur (41.6 g, 1.30 moles) was added with continuedstirring. The sulfur dissolved within several minutes, accompanied by amodest increase in temperature, to form a deep reddish-brown solution.Tetraethoxysilane (624.9 g, 3.0 moles) was then added to the solutionwith continued stirring and the solution was brought to reflux andmaintained for several hours. Heating was discontinued and3-chloro-1-propyltriethoxysilane (240 g, 1.00 moles) was slowly added tothe still warm, stirred solution. Within a few minutes, the solutionturned cloudy, and a precipitate of sodium chloride began to form. Therate of addition was adjusted so that the resulting exotherm maintaineda smooth reflux. The reflux subsided shortly after the addition of the3-chloro-1-propyltriethoxysilane was complete, whereupon power wassupplied to the heating mantle to maintain a smooth reflux for anadditional 3 hours. At this point, the reaction and sodium chlorideformation was complete and heating was discontinued. The solution wasallowed to cool to room temperature with continued stirring, and thendecanted in a tall, narrow vessel. The clear liquid was poured off andthe remaining slurry was shaken with fresh ethanol to extract more ofthe soluble product and the decantation and pouring off was repeatedtwice. The resulting three portions of clear liquid were combined. Theprecipitated sodium chloride in this fashion removed from the ethanolicsolution of the hybrid silane. The ethanol was then removed by rotaryevaporation to less than 1 torr at 65° C. This resulted in a turbid,brown liquid consisting of the hybrid silane and some additional sodiumchloride which was dissolved in the ethanol and had thus escaped priorfiltration. The hybrid silane was again filtered to remove the sodiumchloride, resulting in the final product, which was a clear, brownliquid.

GCMS (gas chromatography coupled to mass spectrometry) indicated thepresence of tetraethoxysilane (44.4%),bis(3-triethoxysilyl-1-propyl)disulfide together with smaller amounts ofthe trisulfide and thioether analogs, tetraethoxysilane condensates,polysulfide silane condensates, and hybrid silanes corresponding tocross condensates of tetraethoxysilane and the polysulfide silanes. Thetetraethoxysilane condensates included hexaethoxydisiloxane (20.6%),octaethoxytrisiloxane (6.5%), together with peaks consistent withsmaller quantities of decaethoxytetrasiloxane,tris-(triethoxysilyl)ethoxysilane,triethoxysilyl-heptaethoxy-cyclotrisiloxane,octaethoxycyclotetrasiloxane, and traces of higher homologs. Thepolysulfide silane condensates included the cyclosiloxane condensationproducts of bis(3-triethoxysilyl-1-propyl)disulfide andbis(3-triethoxysilyl-1-propyl)trisulfide. In addition, there werenumerous peaks in the GC spectrum consistent with the siloxanecross-condensation products of bis(3-triethoxysilyl-1-propyl)polysulfides and tetraethoxysilane, corresponding to the hybrid silanesof the present invention. A partial list of these hybrid silane productsincluded3-triethoxysiloxy-3-diethoxysilyl-1-propyl-3′-triethoxysilyl-1′-propyldisulfide, bis(3-triethoxysiloxy-3-diethoxysilyl-1-propyl)disulfide,bis-(3-triethoxysiloxy)-3-ethoxysilyl-1-propyl-3′-triethoxysilyl-1′-propyldisulfide,bis(3-(3-triethoxysilyl-1-propyldithio)-1-propyldiethoxysiloxy)diethoxysilane,isomers ofbis(3-(3-triethoxysilyl-1-propyldithio)-1-propyldiethoxysiloxy)tetraethoxycyclotrisiloxane,isomers of3-(3-triethoxysilyl-1-propyldithio)-1-propyldiethoxysiloxypentaethoxycyclotrisiloxane,and analogous trisulfide species. Percentages were determined as peakarea percent values.

SFC (supercritical fluid chromatography) analysis using a carbon dioxidemobile phase confirmed the presence of many of the species noted in theparagraph above, along with additional polysulfide species includingbis(3-triethoxysilyl-1-propyl)tetrasulfide,bis(3-triethoxysilyl-1-propyl)pentasulfide,bis(3-triethoxysilyl-1-propyl)hexasulfide,bis(3-triethoxysilyl-1-propyl)heptasulfide, andbis(3-triethoxysilyl-1-propyl)octasulfide; and most combinations oftheir bis-disiloxane condensation products. The presence of theaforementioned hybrid silanes was also confirmed, along with many oftheir higher-sulfur-rank (i.e., tetrasulfide, pentasulfide, etc.)analogs. The higher-sulfur-rank species were only found in the SFCbecause these species are unstable at the high temperatures (up to 250°C.) used in the GC injection port and column.

Example 2 (Silane 2) Preparation of aDimethyldiethoxysilane-bis-(3-triethoxysilyl-1-propyl)polysulfide HybridSilane Composition

The same procedure was used as in Example 1. Hydrous sodium sulfide(60%; 65 g, 0.50 moles) and 500 g of absolute ethanol were introducedinto the 3-liter flask and refluxed with stirring until the flakes haddissolved to give a light yellow-brown, nearly clear solution. Theheating was discontinued and this solution was allowed to cool to 40°C., whereupon powdered sulfur (41.6 g, 1.30 moles) was added withcontinued stirring. The sulfur dissolved within several minutes,accompanied by a modest increase in temperature, to form a deepreddish-brown solution. Dimethyldiethoxysilane (889 g, 6.00 moles) wasthen added to the solution with continued stirring. The solution wasbrought to and maintained at reflux for several hours. Heating wasdiscontinued and 3-chloro-1-propyltriethoxysilane (240 g, 1.00 moles)was slowly added to the still warm, stirred solution. Within a fewminutes, the solution turned cloudy, and a precipitate of sodiumchloride began to form. The rate of addition was adjusted so that theresulting exotherm maintained a smooth reflux. The reflux subsidedshortly after the addition of the 3-chloro-1-propyltriethoxysilane wascomplete, whereupon power was supplied to the heating mantle to maintaina smooth reflux for an additional 3 hours. At this point, the reactionand sodium chloride formation was complete and heating was discontinued.The solution was allowed to cool to room temperature with continuedstirring, and then decanted in a tall, narrow vessel. The clear liquidwas poured off and the remaining slurry was shaken with fresh ethanol toextract more of the soluble product and the decantation and pouring offwas repeated twice. The resulting three portions of clear liquid werecombined. These decantings removed the precipitated sodium chloride fromthe ethanolic solution of the hybrid silane. The ethanol was thenremoved by rotary evaporation to less than 1 torr at 65° C. Thisresulted in a turbid, brown liquid consisting of the hybrid silane andsome additional sodium chloride which had escaped the prior filtrationbecause it had been dissolved in the ethanol. The hybrid silane wasagain filtered to remove the sodium chloride, resulting in the finalproduct, which was a clear, brown liquid.

GCMS analysis indicated the presence of dimethyldiethoxysilane (1.3%),bis(3-triethoxysilyl-1-propyl)disulfide together with smaller amounts ofthe trisulfide and thioether analogs, dimethyldiethoxysilanecondensates, polysulfide silane condensates, and hybrid silanescorresponding to cross condensates of dimethyldiethoxysilane and thepolysulfide silanes. The dimethyldiethoxysilane condensates included1,1,3,3-tetramethyl-1,3-diethoxydisiloxane (16.9%),1,1,3,3,5,5-hexamethyl-1,3,5-triethoxytrisiloxane (14.3%),1,1,3,3,5,5,7,7-octamethyl-1,3,5,7-tetraethoxytetrasiloxane (6.0%), and1,1,3,3,5,5,7,7,9,9-decamethyl-1,3,5,7,9-pentaethoxypentasiloxane(3.9%), together with smaller quantities of several higher homologs. Thepolysulfide silane condensates included the cyclosiloxane condensationproducts of bis(3-triethoxysilyl-1-propyl)disulfide andbis(3-triethoxysilyl-1-propyl)trisulfide. In addition, there werenumerous peaks in the GC spectrum consistent with the siloxanecross-condensation products ofbis(3-triethoxysilyl-1-propyl)polysulfides and dimethyldiethoxysilane,corresponding to the hybrid silanes of the present invention. A partiallist of these hybrid silane products included3-ethoxydimethylsiloxy-3-diethoxysilyl-1-propyl-3′-triethoxysilyl-1′-propyldisulfide,bis(3-ethoxydimethylsiloxy-3-diethoxysilyl-1-propyl)disulfide,bis-(3-ethoxydimethylsiloxy)-3-ethoxysilyl-1-propyl-3′-triethoxysilyl-1′-propyldisulfide,bis(3-(3-triethoxysilyl-1-propyldithio)-1-propyldiethoxysiloxy)dimethylsilane,isomers ofbis(3-(3-triethoxysilyl-1-propyldithio)-1-propyldiethoxysiloxy)tetramethylcyclotrisiloxane,isomers of3-(3-triethoxysilyl-1-propyldithio)-1-propyldiethoxysiloxyethoxytetramethylcyclotrisiloxane,and analogous trisulfide species. Percentages were determined as peakarea percent values.

SFC analysis using a carbon dioxide mobile phase confirmed the presenceof any of the species noted in the paragraph above, along withadditional polysulfide species includingbis(3-triethoxysilyl-1-propyl)tetrasulfide,bis(3-triethoxysilyl-1-propyl)pentasulfide,bis(3-triethoxysilyl-1-propyl)hexasulfide,bis(3-triethoxysilyl-1-propyl)heptasulfide, andbis(3-triethoxysilyl-1-propyl)octasulfide; and most combinations oftheir bis-disiloxane condensation products. The presence of theaforementioned hybrid silanes was also confirmed, along with many oftheir higher-sulfur-rank (i.e. tetrasulfide, pentasulfide, etc.)analogs. The higher-sulfur-rank species were only found in the SFCbecause these species are unstable at the high temperatures (up to 250°)used in the GC injection port and column.

Examples 3 and 4

The hybrid silane compositions prepared in Examples 1 and 2 were used asthe coupling agents to prepare low rolling resistance tire treadformulations. The rubber composition used was the following, where thefigures listed under the PHR heading indicate the mass of thecorresponding ingredient used relative to 100 total mass units ofpolymer (in this case, SSBR and polybutadiene) used:

PHR Ingredient 75 SSBR (12% styrene, 46% vinyl, T_(g): 42° C.) 25cis-1,4-polybutadiene (98% cis, T_(g): 104° C.) 80 Silica (150–190m²/gm, ZEOSIL ® 1165MP, Rhone-Poulenc) 32.5.1.1 Aromatic process oil(high viscosity, Sundex ™ 8125, Sun Oil Co., Inc. (Sunoco)) 2.5 Zincoxide (KADOX ™ 720C, Zinc Corp) 1 Stearic acid (INDUSTRENE ™, CromptonCorp.) 2 6PPD antiozonant (SANTOFLEX ™ 6PPD, Flexsys Corp.) 1.5Microcrystalline wax (M-4067, Schumann Inc.) 3 N330 carbon black(Engineered Carbons, Inc.) 1.4 Sulfur (#104, Sunbelt Co.) 1.7 CBSaccelerator (SANTOCURE ™, Flexsys Corp.) 2 DPG accelerator (PERKACIT ™DPG-C, Flexsys Corp.)

The hybrid silane compositions prepared by the procedures described inExamples 1 and 2 were used to prepare the rubber compositions describedin Examples 3 and 4, respectively. A control was run side by side withExamples 3 and 4 to provide a meaningful basis of comparison for theperformance as a coupling agent in silica-filled rubber of therepresentative examples presented herein of the hybrid silanecompositions. The silane used in the control was the current industrystandard coupling agent for rubber for silica-filled tire treads, thenominal bis(3-triethoxysilyl-1-propyl)tetrasulfide (TESPT). The rubbercompounding formulations and procedures used in Examples 3 and 4 and inthe control were identical with exceptions only in the hybrid silanecomposition used as the coupling agent and in the loading levels of thehybrid silane composition used and the elemental sulfur used in thecuratives. Two rubber formulations were prepared and evaluated in eachof Example 3 and Example 4, corresponding to the two sets of columns inTable 1 under the headings, Example 3 and Example 4. The first of eachof the two sets of columns describes a rubber formulation in which theloading of hybrid silane composition was chosen so as to deliver aconstant loading of sulfur silane silicon, relative to the control. Thismeans that only the silicon from the sulfur silane portion of the hybridsilane composition, only the F¹ portion of Formula (I), was consideredand that the silicon from the alkylalkoxy silane portion of the hybridsilane composition, the F² portion of Formula (I), was disregarded. Therationale for this was that the sulfur silane portion of the couplingagent is the one which actually couples polymer to filler. The second ofeach of the two sets of columns describes the other extreme, which is arubber formulation in which the loading of hybrid silane composition waschosen so as to deliver a constant loading of total silicon from thehybrid silane composition, relative to the control. This means that boththe silicon from the sulfur silane portion of the hybrid silanecomposition, the F¹ portion of Formula (I), and the silicon from thealkylalkoxy silane portion of the hybrid silane composition, the F²portion of Formula (I), were considered. The rationale for this was thatall of the silicon of the coupling agent has the potential to becomeinvolved in polymer to filler coupling in that all of the silicon isexpected to couple at least to the filler, and thereby, indirectly alsoto the polymer by virtue of the Si—O—Si bonds within the hybrid silanes,which link the alkylalkoxy portion of the coupling agent to the sulfursilane portion. The loadings of elemental sulfur in the curatives wereadjusted so as to maintain a constant level, relative to the control, oftotal sulfur delivered to the formulation. Thus, actual loadings ofcoupling agent and elemental sulfur varied due to what amounts toequivalent weight differences among the coupling agents evaluated.

The samples were prepared using a “Model B BANBURY”™ (Farrell Corp.)mixer with a 103 in³ (1690 cc) chamber volume. A rubber masterbatch wasprepared in a two step procedure. The mixer was set at 120 rpm with thecooling water on full. The rubber polymers were added to the mixer whilerunning and ram down mixed for 30 seconds. Approximately half of thesilica (about 35 to 40 g), and all of the hybrid silane composition (inan ethylvinyl acetate (EVA) bag) were added and ram down mixed for 30seconds. The remaining silica and the oil (in an EVA bag) were thenadded and ram down mixed for 30 seconds. The mixer throat was dusteddown three times and the mixture ram down mixed for 15 seconds eachtime. The mixing speed was increased to between about 160 to about 240rpm as required to raise the temperature of the rubber masterbatch tobetween about 160 and about 165° C. in approximately 1 minute. Themasterbatch was removed from the mixer and using this composition, asheet was then formed on a roll mill set at about 50 to about 60° C.,and then allowed to cool to ambient temperature.

The masterbatch was then again added to the mixer with the mixer at 120rpm and cooling water turned on full and ram down mixed for 30 seconds.The remainder of the ingredients were then added and ram down mixed for30 seconds. The mixer throat was dusted down, and the mixer speed wasincreased to about 160 to about 240 rpm in order to increase thetemperature of the mix to about 160 to about 165° C. in approximately 2minutes. The rubber composition was mixed for 8 minutes with adjustmentsto the mixer speed in order to maintain the temperature between about160 to about 165° C. The composition was removed from the mixer and asheet about inch thick was formed on a 6×12 inch roll mill set at about50 to about 60° C. This sheet was then allowed to cool to ambienttemperature.

The resulting rubber composition was subsequently mixed with thecuratives on a 6 in.×13 in. (15 cm×33 cm) two roll mill that was heatedto between 50 and 60° C. The sulfur and accelerators were then added tothe composition and thoroughly mixed on the roll mill and allowed toform a sheet. The sheet was cooled to ambient conditions for about 24hours before it was cured.

The rheological properties of the rubber compound so prepared weremeasured on a Monsanto R-100 Oscillating Disk Rheometer and a MonsantoM1400 Mooney Viscometer. A Rheometrics ARES was used for dynamicmechanical analysis. The specimens for measuring the mechanicalproperties were cut from 6 mm plaques cured for 35 minutes at 160° C. orfrom 2 mm plaques cured for 25 minutes at 160° C. The hybrid silanecompositions, whose preparations were described in Examples 1 and 2,were compounded into the tire tread formulation according to the aboveprocedure. In Example 3, the hybrid silane composition prepared inExample 1 was used, and in Example 4, the hybrid silane compositionprepared in Example 2 was used.

These examples were tested against a control sample which is nominallybis-(3-triethoxysilyl-1-propyl)tetrasulfide (TESPT), an industrystandard coupling agent. Its actual composition is a mixture ofpolysulfides, with significant contributions from individual speciescontaining chains of from 2 to 8 sulfur atoms. The compositions weretested using standard testing procedures. The results of the testing aresummarized in Table 1 below.

Test Methods

-   1. Mooney Scorch    -   ASTM D1646.-   2. Mooney Viscosity    -   ASTM D1646.-   3. Oscillating Disc Rheometer (ODR)    -   ASTM D2084.-   4. Physical Properties: Storage Modulus, Loss Modulus, Tensile &    Elongation    -   ASTM D412 and D224.-   5. DIN Abrasion    -   DIN Procedure 53516.-   6. Heat Buildup    -   ASTM D623.    -   Heat build-up was measured at 100° C. using an 18.5%        compression, 143 psi load and a 25 minute run. A sample which        was at ambient conditions was placed in an oven that had been        preheated to 100° C. The sample was conditioned at 100° C. for        20 minutes and then given a 5 minute test run.-   7. % Permanent Set    -   ASTM D623.-   8. Shore A Hardness    -   ASTM D2240.

TABLE 1 Properties and Processing Parameters of Rubber Compounded inExamples 3 and 4 Using the Coupling Agents Prepared in Examples 1 and 2,Respectively Example 3 Example 4 Control Silane: Type and Amount Silane1 Silane 2 TESPT Silane Loading (phr) 18.3 7.0 10.0 7.0 7.0 ElementalSulfur in Curatives (phr) 1.4 2.35 1.4 1.86 1.4 Mooney Viscosity @ 100°C. (ML1 + 4) 81 69 93 71 73 Mooney Scorch @ 135° C., minutes MS1 + t₃6.6 7.7 6.6 8.0 6.3 MS1 + t₁₈ 8.3 9.7 7.5 9.3 8.6 MS1+ 51.7 35.1 57.440.8 43.2 ODR @ 149° C., 1° Arc; 30 minutes M_(L), dN-m 10.5 9.2 10.79.3 9.0 M_(L), lb-in 9.3 8.1 9.5 8.2 8.0 M_(H), dN-m 37.6 36.4 37.6 38.331.1 M_(H), lb-in 33.3 32.2 33.3 33.9 27.5 t_(s1), minutes 4.1 4.8 3.94.9 4.1 t₉₀, minutes 15.4 17.6 13.6 16.3 18.0 Physical Properties; 90minute cure @ 149° C. Shore A Hardness 61 62 62 63 58 % Elongation 357416 430 382 406 25% Modulus, Mpa 25% Modulus, psi 100% Modulus, Mpa 2.522.35 2.19 2.63 1.91 100% Modulus, psi 365 341 318 381 277 200% Modulus,Mpa 7.50 6.87 6.36 7.85 5.72 200% Modulus, psi 1088 996 922 1138 829300% Modulus, Mpa 14.83 14.09 12.89 15.26 12.62 300% Modulus, psi 21502043 1869 2212 1830 400% Modulus, Mpa 21.25 19.54 20.05 400% Modulus,psi 3081 2833 2907 Tensile Strength, Mpa 18.98 22.24 21.48 21.55 20.49Tensile Strength, psi 2752 3225 3115 3125 2971 Reinforcement Index(300%/25% Mod.) Reinforcement Index (300%/100% Mod.) 5.88 6.00 5.89 5.806.61 Dynamic Mechanical Analysis @ 0.15% Strain, torsion mode (2^(nd)sweep) G′ ×10⁻⁷, dyn/cm²; @ 0° C., 1 Hz 6.8083 7.4502 4.5625 10 Hz8.4568 9.3692 5.7529 G′ ×10⁻⁷, dyn/cm²; @ 60° C., 1 Hz 3.4851 3.32692.2990 10 Hz 3.8918 3.8142 2.6401 G″ ×10⁻⁷, dyn/cm²; @ 0° C., 1 Hz0.9933 1.1598 0.7111 10 Hz 1.6753 1.9041 1.2383 G″ ×10⁻⁷, dyn/cm²; @ 60°C., 1 Hz 0.2645 0.3036 0.2050 10 Hz 0.3315 0.3961 0.2720 Tan Delta @ 0°C., 1 Hz 0.1459 0.1557 0.1559 10 Hz 0.1981 0.2032 0.2153 Tan Delta @ 60°C., 1 Hz 0.0759 0.0913 0.0892 10 Hz 0.0852 0.1039 0.1030 Ratio of TanDelta (0° C./60° C.), 1 Hz 1.922 1.705 1.748 10 Hz 2.325 1.956 2.090Dynamic Mechanical Analysis @ 3% Strain, torsion mode (2^(nd) sweep) G′×10⁻⁷, dyn/cm²; @ 0° C., 1 Hz 4.2296 4.3388 10 Hz 5.1007 5.1404 G′×10⁻⁷, dyn/cm²; @ 60° C., 1 Hz 2.7121 2.7545 10 Hz 2.9899 3.0569 G″×10⁻⁷, dyn/cm²; @ 0° C., 1 Hz 0.9985 1.0953 10 Hz 1.6027 1.6157 G″×10⁻⁷, dyn/cm²; @ 60° C., 1 Hz 0.2900 0.3502 10 Hz 0.3696 0.4559 TanDelta @ 0° C., 1 Hz 0.2361 0.2524 10 Hz 0.3142 0.3143 Tan Delta © 60°C., 1 Hz 0.1069 0.1271 10 Hz 0.1236 0.1491 Ratio of Tan Delta (0° C./60°C.), 1 Hz 2.209 1.986 10 Hz 2.542 2.108 Heat Build-up, 100° C., 17.5%Compression, 990 Kpa (143 psi) static load, 25 minute run Delta T, ° C.29 25 22 22 23 % Permanent Set 10.3 9.9 6.2 6.2 6.2 Unit Conversions: 1Mpa (megapascal) = 10⁶ N/m² = 10⁷ dyn/cm² = 145.0377 psi 1 psi = 68947.6dyn/cm² 1 lb-in = 1.13 dN - m

The present invention offers an alternative route to analogs of theaforementioned coupling agents whereby hydrated sodium sulfide,polysulfide, and hydrosulfide salts can be used as raw materials. Themolecular structure of the coupling agents is altered at the siliconatom but not at the sulfur atom relative to that of the coupling agentsderived from prior art anhydrous sodium sulfide, polysulfide, andhydrosulfide salts. This altered molecular structure can furthermore beused to advantage by proper adjustment of the manufacturing process toyield coupling agents which perform better than the analogs prepared bycurrent conventional methods.

1. A hybrid silane composition comprising a mixture of compoundscorresponding to the general formula:F¹ _(r)F² _(s)  Formula (I) wherein r is 0 to 10,000; s is 0 to 10,000;with the proviso that r has a value of 1 to 2 and s has a value of 1 to3 for at least one compound of Formula (I) in the mixture of compounds;F¹ is a sulfur silane structure selected from the group consisting of:{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R²_(n)Si-G¹-S_(x)—(C=E)_(y)-E_(z)}_(p)-G²  Formula (II) and{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R² _(n)Si-G¹-S_(x)—}₂(C=E)_(y)  Formula(III) wherein each occurrence of R¹ and R² is independently hydrogen, orany group which can be obtained by removal of one hydrogen atom from ahydrocarbon group having from 1 to 20 carbon atoms, including branchedor straight chain alkyl, alkenyl, aryl or aralkyl groups; eachoccurrence of G¹ is any group which can be obtained by removal of aquantity of two hydrogen atoms from any hydrocarbon having from 1 to 20carbon atoms; each occurrence of G² is independently a hydrogen atom orany group which can be obtained by removal of a quantity of p hydrogenatoms from any hydrocarbon having from 1 to 20 carbon atoms; S issulfur; O is oxygen; Si is silicon; each occurrence of E isindependently oxygen or S_(x); each occurrence of m can be 1 or 2 and ncan be 0, 1 or 2; each occurrence of p is independently 1 to 4; eachoccurrence of y is 1 and z is independently 0 or 1; and each occurrenceof x is independently 1 to 8; F² is a nonsulfur silane structurerepresented by the general formula:(R¹O)_(4-m′-n′)[(—O—)_(0.5)]_(m′)R³ _(n′)Si  Formula (IV) wherein eachoccurrence of R¹ is as defined above; each occurrence of R³ isindependently hydrogen, or a hydrocarbon group of 1 to 20 carbon atomsincluding aryl as well as branched or straight chain alkyl, alkenyl,arenyl, or aralkyl groups; and each occurrence of m′ can be 1, 2 or 3and n′ can be 0, 1, 2 or
 3. 2. The composition of claim 1 wherein r ands have a value of
 1. 3. The composition of claim 1 wherein the sulfursilane is selected from the group consisting ofbis-(3-triethoxysilyl-1-propyl)dithiocarbonate andbis-(3-triethoxysilyl-1-propyl)trithiocarbonate.
 4. The composition ofclaim 1 wherein the nonsulfur silane is selected from the groupconsisting of tetraethoxysilane, tetramethoxysilane, triethoxysilane,tetraisopropoxysilane, tetrapropoxysilane, methyltriethoxysilane,methyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane,propyltrimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane,octyltriethoxysilane, octyltrimethoxysilane, octadecyltriethoxysilane,and octadecyltrimethoxysilane.
 5. The composition of claims 1 wherein xof Formulas (II) and (III) is 1 to
 8. 6. A process of making a hybridsilane composition comprising the steps of hydrolyzing a sulfur silaneand a nonsulfur silane in the presence of water to effect partialhydrolysis of silane alkoxy groups on each of the sulfur silane andnonsulfur silane, and bonding the partially hydrolyzed sulfur silane andnonsulfur silane to each other via Si—O—Si linkages, said hybrid silanecomposition comprising a mixture of compounds corresponding to thegeneral formula:F¹ _(r)F² _(s)  Formula (I) wherein r is 0 to 10,000; s is 0 to 10,000;with the proviso that r has a value of 1 to 2 and s has a value of 1 to3 for at least one compound of Formula (I) in the mixture of compounds;F¹ is a sulfur silane structure selected from the group consisting of:{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R²_(n)Si-G¹-S_(x)—(C=E)_(y)-E_(z)}_(p)-G²  Formula (II) and{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R² _(n)Si-G¹-S_(x)—}₂(C=E)_(y)  Formula(III) wherein each occurrence of R¹ and R² is independently hydrogen, orany group which can be obtained by removal of one hydrogen atom from ahydrocarbon group having from 1 to 20 carbon atoms, including branchedor straight chain alkyl, alkenyl, aryl or aralkyl groups; eachoccurrence of G¹ is any group which can be obtained by removal of aquantity of two hydrogen atoms from any hydrocarbon having from 1 to 20carbon atoms; each occurrence of G² is independently a hydrogen atom orany group which can be obtained by removal of a quantity of p hydrogenatoms from any hydrocarbon having from 1 to 20 carbon atoms; S issulfur; O is oxygen; Si is silicon; each occurrence of E isindependently oxygen or S_(x); each occurrence of m is 1 or 2 and n is0, 1 or 2; each occurrence of p is independently 1 to 4; each occurrenceof y is 1 and z is independently 0 or 1; and each occurrence of x isindependently 1 to 8; F² is a nonsulfur silane structure represented bythe general formula:(R¹O)_(4-m′-n′)[(—O—)_(0.5)]_(m′)R³ _(n′)Si  Formula (IV) wherein eachoccurrence of R¹ is as defined above; each occurrence of R³ isindependently hydrogen, or a hydrocarbon group of 1 to 20 carbon atomsincluding aryl as well as branched or straight chain alkyl, alkenyl,arenyl, or aralkyl groups; and each occurrence of m′ can be 1, 2 or 3and n′ can be 0, 1, 2 or
 3. 7. The process of claim 6 wherein the sourceof water is selected from the group consisting of water and a hydratedchemical species.
 8. The process of claim 7 wherein the hydratedchemical species is an alkali metal salt.
 9. The process of claim 8wherein the alkali metal salt is selected from the group consisting ofhydrated alkali metal sulfide, polysulfide, hydrosulfide salt andmixtures thereof.
 10. The process of claim 6 wherein the mixture ofcompounds comprises at least one member selected from the groupconsisting of a sulfur silane, a sulfur silane condensate, analkylalkoxysilane and an alkylalkoxysilane condensate.
 11. The processof claim 6 wherein the sulfur silane is selected from the groupconsisting of bis-(3-triethoxysilyl-1-propyl)dithiocarbonate andbis-(3-triethoxysilyl-1-propyl)trithiocarbonate.
 12. The process ofclaim 6 wherein the nonsulfur silane is selected from the groupconsisting of tetraethoxysilane, tetramethoxysilane, triethoxysilane,tetraisopropoxysilane, tetrapropoxysilane, methyltriethoxysilane,methyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane,propyltrimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane,octyltriethoxysilane, octyltrimethoxysilane, octadecyltriethoxysilane,and octadecyltrimethoxysilane.
 13. A composition comprising: polymer;filler; and a hybrid silane composition which comprises a mixture ofcompounds corresponding to the general formula:F¹ _(r)F² _(s)  Formula (I) wherein r is 0 to 10,000; s is 0 to 10,000;with the proviso that r has a value of 1 to 2 and s has a value of 1 to3 for at least one compound of Formula (I) in the mixture of compounds;F¹ is a sulfur silane structure selected from the group consisting of:{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R²_(n)Si-G¹-S_(x)—(C=E)_(y)-E_(z)}_(p)-G²  Formula (II) and{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R² _(n)Si-G¹-S_(x)—}₂(C=E)_(y)  Formula(III) wherein each occurrence of R¹ and R² is independently hydrogen, orany group which can be obtained by removal of one hydrogen atom from ahydrocarbon group having from 1 to 20 carbon atoms, including branchedor straight chain alkyl, alkenyl, aryl or aralkyl groups; eachoccurrence of G¹ is any group which can be obtained by removal of aquantity of two hydrogen atoms from any hydrocarbon having from 1 to 20carbon atoms; each occurrence of G² is independently a hydrogen atom orany group which can be obtained by removal of a quantity of p hydrogenatoms from any hydrocarbon having from 1 to 20 carbon atoms; S issulfur; O is oxygen; Si is silicon; each occurrence of E isindependently oxygen or S_(x); each occurrence of m is 1 or 2 and n is0, 1 or 2; each occurrence of p is independently 1 to 4; each occurrenceof y is 1 and z is independently 0 or 1; and each occurrence of x isindependently 1 to 8; F² is a nonsulfur silane structure represented bythe general formula:(R¹O)_(4-m′-n′)[(—O—)_(0.5)]_(m′)R³ _(n′)Si  Formula (IV) wherein eachoccurrence of R¹ is as defined above; each occurrence of R³ isindependently hydrogen, or a hydrocarbon group of 1 to 20 carbon atomsincluding aryl as well as branched or straight chain alkyl, alkenyl,arenyl, or aralkyl groups; and each occurrence of m′ can be 1, 2 or 3and n′ can be 0, 1, 2 or
 3. 14. The composition of claim 13 wherein thesulfur silane is selected from the group consisting ofbis-(3-triethoxysilyl-1-propyl)dithiocarbonate andbis-(3-triethoxysilyl-1-propyl)trithiocarbonate.
 15. The composition ofclaim 13 wherein the nonsulfur silane is selected from the groupconsisting of tetraethoxysilane, tetramethoxysilane, triethoxysilane,tetraisopropoxysilane, tetrapropoxysilane, methyltriethoxysilane,methyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane,propyltrimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane,octyltriethoxysilane, octyltrimethoxysilane, octadecyltriethoxysilane,and octadecyltrimethoxysilane.
 16. The composition of claim 13 whereinthe polymer comprises sulfur vulcanizable rubber.
 17. The composition ofclaim 13 wherein the filler is selected from the group consisting ofsiliceous fillers, carbon black and mixtures thereof.
 18. A process ofmaking a sulfur vulcanized rubber product which comprises: mixing sulfurvulcanizable rubber, filler and a hybrid silane composition to form amixture, said hybrid silane composition comprising a mixture ofcompounds corresponding to the general formula:F¹ _(r)F² _(s)  Formula (I) wherein r is 0 to 10,000; s is 0 to 10,000;with the proviso that r has a value of 1 to 2 and s has a value of 1 to3 for at least one compound of Formula (I) in the mixture of compounds;F¹ is a sulfur silane structure selected from the group consisting of:{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R²_(n)Si-G¹-S_(x)—(C=E)_(y)-E_(z)}_(p)-G²  Formula (II) and{(R¹O)_(3-m-n)[(—O—)_(0.5)]_(m)R² _(n)Si-G¹-S_(x)—}₂(C=E)_(y)  Formula(III) wherein each occurrence of R¹ and R² is independently hydrogen, orany group which can be obtained by removal of one hydrogen atom from ahydrocarbon group having from 1 to 20 carbon atoms, including branchedor straight chain alkyl, alkenyl, aryl or aralkyl groups; eachoccurrence of G¹ is any group which can be obtained by removal of aquantity of two hydrogen atoms from any hydrocarbon having from 1 to 20carbon atoms; each occurrence of G² is independently a hydrogen atom orany group which can be obtained by removal of a quantity of p hydrogenatoms from any hydrocarbon having from 1 to 20 carbon atoms; S issulfur; O is oxygen; Si is silicon; each occurrence of E isindependently oxygen or S_(x); each occurrence of m is 1 or 2 and n is0, 1 or 2; each occurrence of p is independently 1 to 4; each occurrenceof y is 1 and z is independently 0 or 1; and each occurrence of x isindependently 1 to 8; F² is a nonsulfur silane structure represented bythe general formula:(R¹O)_(4-m′-n′)[(—O—)_(0.5)]_(m′)R³ _(n′)Si  Formula (IV) wherein eachoccurrence of R¹ is as defined above; each occurrence of R³ isindependently hydrogen, or a hydrocarbon group of 1 to 20 carbon atomsincluding aryl as well as branched or straight chain alkyl, alkenyl,arenyl, or aralkyl groups; and each occurrence of m′ can be 1, 2 or 3and n′ can be 0, 1, 2 or 3; and curing the mixture in the presence of asulfur source to provide the sulfur vulcanized rubber product.
 19. Theprocess of claim 18 wherein the product is employed in the constructionof a tire.
 20. The process of claim 6 wherein r and s have a value of 1.21. The process of claim 18 wherein r and s have a value of 1.